minor changes to null checks. Not even sure that the change looks better than the original
catching up with Jen's change https://github.com/jmoenig/morphic.js/commit/e936e9d41023e954b307107431e1428a20687a52 ...

Menu items can now be labelled by a string, a multi-line string
(containing line breaks), icons (of type Morph or Canvas) or
icon-string pairs
catching up with Jens' https://github.com/jmoenig/morphic.js/commit/c9d22f74c57e4ecaf3b6b28b8255bfcd17a35ba3 ...

new slider edit event & updated documentation
new event: reactToSliderEdit() allows for "live coding" apps. Updated
documentation with a new section about text editing events.
catching up with Jens' https://github.com/jmoenig/morphic.js/commit/03d54fbc98cf0123c4afa111a79c8c871ead3646 ...

support for detecting dropped binary files
new event: droppedBinary(aBinaryString, name)
rebuild and docs